Claddings are often applied to equipment subjected to harsh environments or operating conditions in efforts to extend the useful lifetime of the equipment. Various cladding identities and constructions are available depending on the mode of failure to be inhibited. For example, wear resistant, erosion resistant and corrosion resistant claddings have been developed for metallic substrates. Moreover, metal or alloy claddings can be applied to metallic substrates by a variety of techniques including weld overlay, plasma transferred arc, thermal spray, laser cladding, infrared cladding, induction cladding or sintering.
A significant problem encountered in cladding applications is premature failure or degradation of the cladding. Claddings of metallic substrates can fail according to a variety of mechanisms, including delamination and cracking/fracture. In some cases, a cladded metal substrate is subjected to thermal cycling that can impair the bonding of the cladding to the substrate. In some applications, for example, the metal substrate is subjected to a post-coat heat treatment such as normalizing in order to improve the mechanical properties of the substrate, wherein the post-coat heat treatment fractures the cladding. Moreover, in some cases, shrinkage of the cladding during deposition can induce cracking and/or delamination. Such shrinkage is exacerbated by metallic articles having complex geometries, including frack valves.
Frack valves are employed in high pressure positive displacement or reciprocating pumps often used in hydraulic fracturing and/or other earth boring applications. Given this high wear environment, frack valves can benefit from erosion resistant claddings. However, complex frack valve geometry places restrictions on cladding techniques and cladding composition. Hardfacing alloys applied by sintering, for example, exhibit unacceptable cracking and delamination along seat surfaces. FIGS. 1A and 1B illustrate such cracking for sintered cobalt alloy STELLITE®12 applied to a frack valve. Cracking and delamination occurs along the ID and OD edges of the seat surfaces. These defects can frustrate the use of hardfacing alloys having high hardness and high wear resistance.